MMG simply stated, is the sound that resonates from the muscle during a stimulated contraction. The act of pulling on a taught string and letting go has been related to model the sound generated by the muscle. This sound can be caused by the cycling of the actin myosin cross bridges, or perhaps by the gross lateral shift of the muscle, or maybe even the brief shock generated by the thickening of several active muscle fibers. These are three of the hypothesis that try to account for the sound emitted from the muscle. The exact cause of mechanomyography is yet to be determined, but there are a few attributes that can be spoken for. It is understood that ‘the muscle sound is related to muscle activity and its properties are related to the properties of the contraction.’ (8) The main frequency of MMG is 25 Hertz, British physicist, chemist, and physician William Wollaston determined this. This can possibly be attributed to the ATP turnover rate. ATP can hydrolyze and refurbished at a rate of about 40msec, which translates into 25Hertz. (8,10)
The MMG signal can be recorded using a variety of transducers. One is the piezoelectric crystal contact sensor (microphone). Some researchers have used a hydrophone in studies when the muscle was submerged in water in vivo, others have used condensers.(11) It will be discussed later some of the differences between the types.
Factors that influence the MMG signal can include stiffness of the muscle, fluid in an around the muscle, temperature of the tissue, fiber type, gender, technique and equipment used, type of contraction performed, amount of fatigue, and cross talk between muscles.
Stiffness can alter the MMG by lowering the amplitude. As the muscle produces a greater force the stiffness of the muscle increases linearly with the force increase. When subject reaches 80 – 100% of MVC this stiffness can cause the amplitude of the signal to decrease due to the fusion of motor unit twitches, which will limit the oscillation.(2) This stiffness can also be attributed when talking about the different types of contraction.
Types of contraction have been shown to provoke different amounts of peak torque. Eccentric forms of contraction elicit greater force production than that of concentric. This could cause a greater stiffness in the muscle during eccentric contractions, which could lower the MMG. Also there is the mechanism behind the contraction that could be the factor.
In lab, isometric handgrip strength was tested. Isometric strength refers to the type of force that occurs when muscles generate force, but its length remains unchanged. This can also be called a static muscle contraction. A static contraction occurs when one tries to lift an object that happens to be heavier than the force applied to the muscle or a static contraction occurs when one supports the weight of an object by holding the object steady with the elbow flexed. In both of these examples, the person feels their muscles tense but the joint does not move (Kenney, Wilmore, & Costill, 2012). Handgrip strength reflects the importance for successful performance in activities of daily living and occupational activities (Beam &
The subject’s forearm was prepared by cleaning the surface of their skin (the flexor digitorum superficialis muscle) and the bony prominence of their wrist with an alcohol swab, and the EMG adhesive electrodes where placed on the belly of the flexor digitorum superficialis muscle. The positive electrode was placed more proximal to the elbow, while the negative electrode was placed more mid-distally. The grounding (noise reducing) electrode was places on the bony prominence of the wrist, and the force transducer was setup to achieve a stable baseline. The subject was then instructed to the support their forearm over the edge of the table or on their leg with the wrist in a semi-flexed position, and when ready squeeze the force grip transducer as hard as possible. For the first/”fast” time interval of the experiment, the subject made ten squeezes as fast as possible with one second per squeeze intervals, and the force onset, EMG onset, difference between force onset and EMG onset, peak EMG amplitude, and peak force amplitude were observed and recorded. The experiment was then repeated for a medium, three seconds per squeeze, and slow, five seconds per squeeze time intervals with the same variables observed and
Every day we use our skeletal muscle to do simple task and without skeletal muscles, we will not be able to do anything. Szent-Gyorgyi (2011) muscle tissue contraction in rabbit’s muscles and discovered that ATP is a source for muscle contraction and not ADP. He proposed a mechanism to cellular respiration and was later used by Sir Hans Krebs to investigate the steps to glucose catabolism to make ATP. In this paper, I will be discussing the structure of muscle fibers and skeletal muscles, muscle contraction, biomechanics, and how glucose and fat are metabolized in the skeletal muscles.
Muscle is a very specialized tissue that has both the ability to contract and the ability to conduct electrical impulses. Muscle fiber generates tension through the action of actin and myosin cross-bridge cycling. The muscle may shorten, lengthen or remain the same under tension. Skeletal muscle has an impressive ability to regenerate itself, which it does on a daily basis as well as in response to injury [1].
Myasthenia Gravis is an autoimmune neuromuscular disorder. The term "myasthenia" is Latin for muscle weakness, and "gravis" for grave or serious. It is characterized by random weakness of voluntary muscle groups. Muscle groups most commonly affected include the eye muscles, facial, chewing and swallowing muscles, and shoulder and hip muscles. It is typical for a myasthenic patient to have a flattened smile, droopy eyes and an ineffective cough due to weak expiratory muscles, are all also associated with MG. Most myasthenic patients usually don't complain of extensive feelings of fatigue. They experience localized fatigue in specific, repeatedly used muscles. Today, MG is one of the most thoroughly understood neurological disorders, which has lead to treatments, which enormously improves the length and quality of life of myasthenics.
As we have learned through our reading, most all bodies skeletal muscles are made up of primarily three types of skeletal muscle fibers, but their proportion differs depending on what action the muscles is doing. For example, type I fibers such as muscles of the neck, back, and leg have a higher proportion. According to Quinn (2014), type I muscles are slower and more effective, they tend fire a lot slower than fast twitch fibers and they fatigue at a much slower rate. Hence, slower twitch fibers are pronounced at helping athletes run marathons and bicycle for hours. Shoulder and arm muscles are not always active but are intermittent in their use; these muscles tend to have a larger amount of tension for uses in throwing and lifting. These muscles have a combination of both type I and type II B fibers. These fast twitch fibers use anaerobic metabolism to create energy and are the "classic" fast twitch muscle fibers that excel at producing quick, powerful bursts of speed. These muscles are used in events such as 100m sprint, basketball, soccer and football. Since this muscle fiber fires at such a high rate of contraction it will fatigue much faster and will not last long before needing to rest.
Sarcopenia is considered to be the degenerative loss of skeletal muscle mass and it’s functioning due to aging (Waters, Baumgartner & Garry 2000). It is linked to muscle atrophy which is shortening of the muscle. It can be mostly noticed in fast twitch fibres which usually fatigue easily and provide a larger amount of force in comparison to slow twitch fibres. Sarcopenia is usually ...
...gth of contraction: The muscle can be fine or coarse depending on the amount of motor units connected to muscle fibers. For example, the fine muscles contract faster because of higher number of motor units. The length of muscle in terms of its sarcomeres has an effect on the contraction length. The actions potentials have to get farther along and reach more sarcomeres to have them contract (Q3) [1], [2].
...en and elastin. Studies have shown that exercise prevents changes in collagen and elastin which leads to stiffness. Exercise also prevent accumulation of advanced glycation end-product which increases with age and is known to cause stiffness.
The skeletal and ultimate cardiac muscle fibers are affected by DMD. The disease starts by affecting the lower port...
When a muscle contracts and relaxes without receiving signals from nerves it is known as myogenic. In the human body, the cardiac muscle is myogenic as this configuration of contractions controls the heartbeat. Within the wall of the right atrium is the sino-atrial node (SAN), which is where the process of the heartbeat begins. It directs consistent waves of electrical activity to the atrial walls, instigating the right and the left atria to contract at the same time. During this stage, the non conducting collagen tissue within the heart prevents the waves of electrical activity from being passed directly from the atria to the ventricles because if this were to happen, it would cause a backflow. Due to this barrier, The waves of electrical energy are directed from the SAN to the atrioventricular node (AVN) which is responsible for transferring the energy to the purkyne fibres in the right and left ventricle walls. Following this, there is a pause before the wave is passed on in order to assure the atria has emptied. After this delay, the walls of the right and left ventricles contract
o If a stimulus was strong enough to excite contraction, it produced a maximal contraction
in soft tissue mobilization pressure.” Medicine and Science in Sports and Exercise. April 1999: 531-5.
Cardiac muscle is a type of involuntary muscle found only in the walls of the heart, specifically the myocardium. Cardiac muscles contract automatically to tighten the walls of the heart in a rhythmic fashion (pp.212-216). The heart beats nonstop about 100,000 times each day (p.18). Smooth muscle is a type of involuntary muscle found within the walls of blood vessels such as in small arteries and veins. Smooth muscle is also found in the urinary bladder, uterus, male and female reproductive tracts, gastrointestinal tract, and the respiratory tract. Skeletal muscles are voluntarily controlled and are attached to bones by tendons. Skeletal muscles also vary considerably in size and shape. They range from extremely tiny strands such as in the muscle of the middle ear as large like in the muscles of the thigh (Martini, 2000). The three individual muscle types also serve five main functions. The five basic functions are movement, organ protection, pumping blood, aiding digestion, and ensuring blood flow.
The muscular system is a very important part of the human body. It has many components and functions, and is the source of the body’s movement. There are roughly 650 muscles in the human body and are different types of muscles. Muscles can either be voluntary or involuntary which means controlled or uncontrolled movement. Muscles have many reasons and in this paper you will widen your knowledge of muscles and their functions as well their diseases and how they help maintain the body.